Hitherto, there has been known a stepless transmission in which an endless transmission member composed of a band-like belt is wound between an input pulley and an output pulley, and the gear ratio is changed by changing the widths of the V-grooves of the input pulley and the output pulley (refer to, for example, Japanese Translation of PCT International Application Publication No. 2005-506500).
According to the stepless transmission described in Japanese Translation of PCT International Application Publication No. 2005-506500, a ball screw is provided in a rotating shaft so as to maintain the travel distances of the right and left halves of a pulley to be equal by the ball screw, thereby preventing the endless transmission member from being distorted.